A2289 board stuck permanently in DFU state

[sekidata]

This 820-01987 board came with damage to the USB-connector, a shorted audio amplifier, and a liquid damaged backlight FET. After correcting these issues, the board is now stuck at 5V USB-C with PPBUS at 12.3V.

When connected to another Mac, it immediately shows DFU mode and appears to be stuck that way. When I hold PMU_ONOFF_L to ground, DFU mode disappears after a few seconds, then immediately comes back on.

DFU Revive and Restore fail with the error "Unexpected device state 'DFU' expected 'Recovery' (Probably forced into DFU mode externally)".

I tried installing the SOC ROM chip U4770 from another board but the same occurs.

 

[2informaticos]

Try soldering an empty U4770.

 

[sekidata]

You mean clearing out the ROM programming and then installing it?

 

[2informaticos]

I said empty (full with FF), not programmed.
The SoC ROM is automatically reprogrammed in DFU process.

 

[sekidata]

Ok, done. This worked in the sense that it allowed me to do a DFU Revive. But now the machine opens to a network selector and always ends with startup error -3400F. It doesn't respond to any startup key combinations. I also cannot get the machine back into DFU mode for a Restore.

 

[2informaticos]

Use external switch method to access DFU mode.

 

[sekidata]

That’s the method I have been using. I ended up erasing the SOC ROM chip again and performing a DFU Restore. But I’m back to the same situation (startup error -3400F).

 

[2informaticos]

Recently I had A2179 model which needed more than 10 tries to get into recovery assistant; always stuck in 2300F error.
I tried ethernet connection, VPN host from my phone and nothing worked.
Second day worked with usual WiFi connection and I can't understand this behavior...